EVALUATION OF FREEZE-THAW METHODS FOR THE REDUCTION OF SALMONELLA TYPHIMURIUM ON RAW PROCESSED POULTRY
Abstract
A repeated freeze-thaw treatment at various rates was evaluated for its effect on cells of Salmonella typhimurium. There was a 99% reduction in the numbers of cells of S. typhimurium suspended in 50 ml of 0.1% peptone after a five cycle rapid freeze-rapid thaw treatment. Portions of chicken wings, consisting of ulna and radius with attached skin and muscle, were inoculated with low (16-20 CFU/g) and high (ca. 1,100 CFU/g) numbers of S. typhimurium (CFU = colony forming units). After treatment with a five cycle rapid freeze-rapid thaw process, there was over a 90% reduction in numbers of bacterial cells of both concentrations of cells inoculated on chicken wings. Chemical treatment of chicken wings inoculated with S. typhimurium was used in conjunction with a five cycle rapid freeze-rapid thaw process. Chemicals used were: 20 ppm chlorine, 5% potassium sorbate, 5% lactic acid, and 5% calcium propionate. There was a 98% reduction of S. typhimurium numbers when chicken wings were treated with 5% lactic acid plus freeze-thaw process, a 96% reduction by 5% calcium propionate plus freeze-thaw process, a 96% decrease by 5% potassium sorbate plus freeze-thaw, a 95% decrease by chlorine plus freeze-thaw, and 95% reduction by a five cycle rapid freeze-rapid thaw treatment. There were no statistically significant differences among the treatments. In a pilot plant study to simulate commercial conditions, a carbon dioxide freezer was used for the rapid freeze and a microwave oven was used for the rapid thaw. Chicken wings treated with 5% lactic acid and subjected to a five cycle rapid freeze-rapid thaw process had statistically significantly fewer surviving S. typhimurium colonies when compared to lactic acid treated wings without being subjected to a freeze-thaw process and to the freeze-thaw process without chemical treatment. Chicken wings treated with 5% lactic acid in conjunction with and without the freeze-thaw process were stored at 2(DEGREES)C for 22 days. The freeze-thaw process did not increase the shelf-life when compared to the control. Lactic acid treatment or lactic acid plus freeze-thaw treatment of wings extended the shelf-life of the wings when compared to the control or freeze-thaw treated wings.
Degree
Ph.D.
Subject Area
Food science
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